Electrical apparatus



Sept. 1, 1953 T. TOG N 0 LA ELECTRICAL APPARATUS F iled Sept. 24, 1951 J mgvro'k.

AT TORNEY.

Patented Sept. 1, 1953 ELECTRICAL APPARATUS Tilllio Tognola, Sidney, N. Y.', assignor to" Bendix Aviation Corporation, New York, N.-Y., a cor-- poration of:Delaware KpplicationSeptember 24, 1951, SerialNo. 2481128" This invention" relates' to"- electrical apparatus andmore particularly to'an electrical circuit for creatingelectric-sparks or arcs-and adapted for use; among other things; an ignition system for combustion engines:

One of the objects of the present invention is to-provide a novel-simplified ignitionor spark producing system which is useful for igniting combustible charges in so' called jet or gas turbine engines, as wellasin-other types of combustion' engines.

Another object oftheinvention is to provide a: novel condenser discharge ty e of ignition circuit wherebya-high-energy sparkor arc may be created between" the electrodes of, a conventional spark plug at" relatively" low voltage;

Still another object is to provide novel means in combination with a condenser-discharge type of circuit for'ionizinga spark or "igniter gap in circuit with a storage condenser'which attains amaximum voltage that is less-than the normal spark-over voltage ofthegap:

The above and furtherobjects and novel features of' thepresent invention will" more fully appear" from the following detail description when the same is readin connectionwith the accompanying drawing. It is to be expressly understood; however; that the drawingis for the purpose of illustration only'and is not intended as a definition of the limitsof-the invention.

In the drawings, wherein likereferencecharacters refer tolike parts-throughout the several views,

Fig. 1 is a diagram illustratin'g'one'form of ignition circuit embodying the invention; and

Fig. 2 is a diagram of anotherform of ignition circuit embodying the invention.

Much difficulty has been experienced in providing a; simple ignition system ofsmallsize and weight which will function satisfactorily to ignite so-calledjet andgas turbineengines under all operating conditions, particularly at high alti tuds while the engine is moving'through space at a high speed. Reasonably successful systems have been heretofore designed,- but all of these have been quite complicated; heavy and spaceconsumingin comparison to the simplified systern comprehended by-this invention;

The-source offelectrical en'ergy' in a circuit embodying thepresent-invention may be of any known type which is:v suitable for chargingan electrical condenser; and in:.-the illustrated embodiment, comprises a storagebatteryifi withone terminal thereoffconnected. togrounc't at 6. The

other terminal of. the battery is connected thrOugh a; manual or power-operated ignition switch 1 to the stationary'contact 8 of a normally closed vibrator switch. The other ter minal or contact 9ofthe vibrator switch is spring mounted or otherwise yieldably' held, as by a spring I 0', in closedposition or in engagement with contact 8. To minimize arcing between separable contacts 8' and 9 asmall condenser. i I may be connected in parallel therewith. Vibrator contact 9 is connected-to and electro niag'net ically actuated in a known manner" by the primary winding I Zofast'ep-up transformer having" a secondary winding l3. Both of said windings are preferably groundedas'at' 6. y

The high potential end of secondary winding I3 is connected through-one ora seriesof haliwa've rectifiers M of any suitable knowntype to a storage condenser IS. The rectifier's' are designed to permit the flow of energy" from winding 13 to condenser I51 without permitting. the condenser to' discharge back" through the winding. The other terminal of condenser I5 is connected to ground; andthe high potential side thereof in addition to being connected to rectifiers I4; is" connected to one terminal of a spark gap 16 which functions. as a control" or triggering gap to control the dischargingof condenser I5 when the" same attains a desirable charge. Control'gapi6 is preferably of scaled type so that the spark-over or break-down-vo1tage thereof remainssubstantiallyconstant' and independent of surrounding pressures and other atmospheric conditions at different altitudes. The other terminal of control gap I6 is connected to parallel branches or circuits,- one of which includes a condenser I! that is smallin comparison to condenser l5and connected inseries with the primary winding lflof a step-up transformer, said primary winding. being connected at one end to-ground. The other said branch or circuitincludes the secondary winding. L9 or said transformer and a" sparkplug or ignitergap 20, one terminal of which may be grounded;

Suitable means, such'as a'resistance 2!; may be connected in shunt with condenser I 1 for the purpose of bleeding off or absorbing any residual charge onsaid" condenser after each operation of the' above=described system inthe manner to beher'einafterexplained. The resistor also dissipa-tesany energy which leaks past con.- trol gap lfi'during the"charging of'condenser I5- to the break-down voltage of'saidfgapn In one practical embodiment of the abovedescribed circuit or system, the source of electrical energy may comprise a standard 24-volt battery 5 which, when switch 7 is closed, causes a current to flow through the normally closed vibrator contacts 8 and 9 to winding :2 and thence to ground at 6, or directly to the low potential terminal of the battery. When winding [2 is thus energized, it functions as an electro-magnet to withdraw movable contact 9 from contact 8 and thereby interrupt the battery circuit. With the winding [2 becoming de-energized upon the opening of vibrator switch 8, 9, the spring 10 is effective to again move contact 9 into engagement with contact 8, and the cycle is repeated. Interrupted direct current which is thus caused to flow through winding :2 is effective to induce a higher voltage across secondary winding !3, the voltage increase being dependent upon the construction of the transformer !2, I3, as is Well understood in the art. In an ignition system for present-day jet-type engines, a voltage of about 5,000 volts or more across secondary winding [3 has been found desirable. Pulses of electrical energy from secondary winding I3 flow through one or a series of rectifiers 4 to charge the storage condenser E5 in increments or steps to a voltage of about 5,000 volts. In such a circuit, three series-connected cold cathode rectifiers each having a hold-off voltage of about 2,000 volts have been found suitable to prevent the discharging of condenser l5 back through winding l3. Sealed gap i6 is so constructed that when condenser l5 attains a charge of about 5,000 volts or other desired voltage, the condenser will discharge across the electrodes of the gap.

The spark-over or break-down voltage of igniter gap 20, which may be the gap between the electrodes of a spark plug in an engine cylinder or other combustion chamber, is normally about 15,000 volts, 1. e., several times greater than the voltage directly available from condenser !5. Accordingly, igniter gap must be first ionized to permit the lower voltage charge from condenser l5 to flow across the same to create the high energy igniting spark. This is accomplished in 9, novel manner by providing the branch circuit !7, 18, which is inductively coupled with branch circuit I9, 20. Upon the initial discharge of storage condenser 15, the capacity of which may be on the order of .1 microfarad, across control gap IS, the smaller condenser [1, having a capacity of about .005 microfarad, is charged very rapidly. The charging current which flows through primary winding it during the charging of condenser ll rises very rapidly or abruptly and accordingly induces a sufiiciently high voltage across secondary winding I!) to ionize spark plug or igniter gap 20. The remainder of the charge on condenser l5 thereupon finds the path of least resistance across ionized gap 20 and creates a high energy spark or are which contains a desired amount of heat for igniting the combustible charge in the engine. The major portion of the charge on condenser I! will also be discharged across the igniter gap.

After each discharge of the condensers l5 and I! in the manner above described, any residual charge on condenser l1 and any energy which leaks past control gap l6 are dissipated in resistance 2!, the ohmic value of which may be about .2 megohm. Thus, upon initiation of each discharge of condenser IS, the condenser ll will be at substantially zero potential so that there will be a maximum voltage differential between the two condensers and hence, a maximum rise in the charging current which flows through coil winding [8 to induce the desired ionizing voltage in circuit branch I9, 20.

If a plurality of igniter gaps 20 are required to be fired in succession or in timed relation, a suitable distributor of known construction may be inserted at a suitable place in the circuit, and the parts on the output side of the distributor, including the igniter gaps may be multiplied in accordance with the number of spark plugs or igniting devices required. If timed discharging of condenser 15 is desired, control gap l6 may be replaced by a cam-operated, normallyopen contactor or equivalent means, such as an electronic valve. One such modification is illus trated in Fig. 2 wherein a magneto 22 of wellknown construction supplies energy to storage condenser 15 through rectifiers I4 and M in a manner well understood in the art. The secondary winding 23 of the magneto coil has a center tap which is grounded at 6' so that current of one polarity flows through rectifiers M and current of the opposite polarity flows through rectifiers M to charge condenser 15 step-by-step or in small increments. The primary winding 24 of the magneto coil is connected in circuit in the usual manner with a circuit breaker 25 across which is connected a condenser 26. The energy stored in condenser I5 is periodically released through a contactor 21 which is normally held in open position by a spring 28 and it intermittently closed by a rotatably driven cam 20. When contactor 21 is closed, condenser 15 will discharge and the resultant operation of the system is the same as that described above in connection with the circuit of Fig. 1. If desired, one set of rectifiers 14 or M may be dispensed with, but in that event the condenser will be charged only half as fast.

There is thus provided a highly efficient and efiective circuit and means for utilizing a low voltage source of electrical energy for producing high energy arcs or sparks across relatively widely separated gap electrodes at a voltage which is substantially below the normal breakdown voltage of the spark or igniter gap. The system provided is more simple and embodies less elements and hence, is less subject to failures in operation than circuits heretofore employed. for attaining similar results. The simplification of the structure also reduces the weight thereof and the space consumed thereby as well as the cost of production and maintenance.

Although only a limited number of embodiments and modifications of the invention have been illustrated and described in the accompanying drawing and foregoing specification, it is to be expressly understood that the invention may be embodied in other specifically different circuits. For example, other well known sources of interrupted, direct or alternating current, such as a generator, may be provided in lieu of the magneto and battery-vibrator combinations illustrated, and other types of rectifiers, such as the selenium type, may be utilized in lieu of the cold cathode or point-to-plane type illustrated. Various other changes may also be made, such as in the electrical values suggested herein by way of example only, without departing from the spirit and scope of the invention, as will now be be apparent to those skilled in the art.

What is claimed is:

1. Electrical apparatus comprising a source of lec al e gy, a transformer comprising primary and secondary windings, a first branch comprising a first condenser connected in series with said primary winding, a second branch comprising a spark gap connected in series with said secondary winding and in parallel with said first branch, a storage condenser, control means for intermittently operatively connecting said storage condenser simultaneously across said branches, and means for connecting said source to said storage condenser to charge the same.

2. Electrical apparatus as defined in claim 1 wherein said source comprises means for charging said storage condenser in increments to a desired voltage.

3. Electrical apparatus as defined in claim 1 wherein said source comprises direct current generating means and a vibrator.

4. Electrical apparatus as defined in claim 1 wherein the source of electrical energy is a generator of alternating current, such as a magneto.

5. Electrical apparatus as defined in claim 1 wherein rectifier means are connected between said source and said storage condenser to prevent discharge of the latter through the source.

6. Electrical apparatus as defined in claim 5 wherein said rectifier means comprises a plurality of half-wave rectifiers connected in series.

7. Electrical apparatus as defined in claim 1 wherein said control means comprises a normally non-conductive electronic valve.

8. Electrical apparatus as defined in claim 1 wherein said control means comprises a normally non-conductive triggering gap.

9. Electrical apparatus as defined in claim 1 wherein said control means comprises a normally open contactor and means for intermittently closing and opening said contactor.

10. Electrical apparatus as defined in claim 1 wherein said control means is adapted to operatively connect said storage condenser across said branches when the charge on said storage condenser reaches a pre-determined voltage.

11. Electrical apparatus as defined in claim 10 wherein the onset voltage of said control means is below the normal spark-over voltage of said spark gap.

12. Electrical apparatus as defined in claim 1 wherein the capacity of said storage condenser is in excess of the capacity of said first condenser.

13. Electrical apparatus as defined in claim 1 comprising a resistance connected in shunt with said first condenser.

14. Electrical apparatus as defined in claim 1 wherein said spark gap has a normal break-down voltage in excess of the voltage attainable by said storage condenser but below the voltage induced in said secondary winding upon discharge of the storage condenser into said first condenser.

TULLIO TOGNOLA.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,197,114 Rabezzana et a1. Apr. 16, 1940 2,589,164 Tognola Mar. 11, 1952 

